Wrapping machine with severing blade in crimping head

Abstract

An article wrapping machine has superposed shafts geared together that mount opposed rotary crimping heads for crimping the wrapping between the articles. A knife blade is radially movable in a slot in the upper crimping head and is projected into a recess in the lower crimping head for severing the wrapping between a string of articles. The blade actuating mechanism comprises a rod axially movable in a bore in the shaft that mounts the upper crimping head. A pair of bell cranks is provided for projecting and retracting the blade. An intermediate portion of each bell crank is pivoted to the crimping head. An outer or free end portion of each crank is pivoted to the blade and the inner ends are pivoted to the rod. The bell cranks are disposed so that the pivotal connections to the blade pass "over center" and the geometry of the arrangement is such that there is virtually no axial or slicing motion of the blade during its radial movement. The blade actuating rod is operated by a cam external of the machine frame which overcomes the force of a spring that is connected directly to the rod and not to the blade. A zig zag severing cut is provided without actually forming the blade as a zig zag member. This is accomplished by beveling one side of the blade and grinding notches in the flat or unbeveled side in a manner that forms specially shaped saw teeth which teeth progressively provide a zig zag severing cut.

What we claim is: 
     
       1. In an article wrapping machine of the type having a frame, superposed shafts geared together and mounting opposed rotary crimping heads for crimping the wrapping between articles, means for mounting a radially movable knife blade in a slot formed in one crimping head, a blade receiving recess formed in the other crimping head, and blade actuating mechanism for moving said blade into and out of said recess to sever the wrapping between articles; the improvement wherein said blade mounting means comprises a pair of axially spaced links pivoted to said blade carrying head at the radially inner portion of its slot, and means connecting an outer end of each of said links to said blade, the shaft mounting said blade carrying head having an axial bore, said blade actuating mechanism comprising a rod movable axially in said shaft bore, the inner end of each of said links being pivotally connected to said rod, cam follower means mounted on one end of said shaft for operating said rod and a stationary cam mounted on said frame for actuating said cam follower means, each of said links comprising a bell crank, the intermediate portion of each bell crank being pivoted to the crimping head, the outer end of each bell crank being pivoted to the blade and the inner end being pivoted to said rod, the blade pivot of each crank, when the blade is retracted, being disposed a short distance radially inwardly of an axial reference line that extends through the axis of the intermediate pivot of the bell crank, said blade pivot being disposed radially outwardly of said reference line by substantailly the same distance when said blade is fully projected. 
     
     
       2. The wrapping machine of claim 1, wherein motion of said blade deviates from pure radial motion by less then 1/64 inches. 
     
     
       3. The wrapping machine of claim 1, wherein said cam surface, said surface being substantially cylindrical but having a single radially inwardly projecting lobe for actuating said cam follower means, said cam lobe having an effective range of action of about 15° of camshaft rotation. 
     
     
       4. The wrapping machine of claim 3, comprising spring means connected directly between said rod and said shaft for causing the rod to retract the blade. 
     
     
       5. The wrapping machine of claim 4, wherein said spring means comprises a tension coil spring disposed in the bore in said shaft, said cam follower means pulling on said rod. 
     
     
       6. The wrapping machine of claim 1, wherein means are provided for adjustably connecting said rod to said cam follower means for precisely positioning said blade. 
     
     
       7. In an article wrapping machine of the type having a frame, superposed shafts geared together and mounting opposed rotary crimping heads for crimping the wrapping between articles, means for mounting a radially movable knife blade in a slot formed in one crimping head, a blade receiving recess formed in the other crimping head, and blade actuating mechanism for moving said blade into and out of said recess to sever the wrapping between articles; the improvement wherein each shaft mounts diametrically opposed crimping heads with both heads on one shaft carrying blades and both heads on the other shaft having recessed, said blade mounting means comprises a pair of axially spaced bell cranks pivoted to each blade carrying head at the radially inner portion of its slot, and means pivotally connecting an outer end of each of said bell cranks to the associated blade, the shaft mounting said blade carrying heads having an axial bore, said blade actuating mechanism comprising two rods movable axially in said shaft bore, the inner end of each of said bell cranks for one blade being pivotally connected to one of said rods, the corresponding bell cranks for the other blade being connected to the other rod, individual cam follower means mounted on one end of said shaft for operating one end of each rod and a stationary cam mounted on said frame for actuating both of said cam followers. 
     
     
       8. The wrapping machine of claim 7, comprising a tension coil spring in said shaft bore connected between the other end of each rod and the shaft, said cam followers pulling on their associated rods. 
     
     
       9. In an article wrapping machine of the type having a frame, superposed shafts geared together and mounting opposed rotary crimping heads for crimping and sealing the wrapping between articles, means for mounting a radially movable knife blade in a slot formed in one crimping head, a blade receiving recess formed in the other crimping head, and blade actuating mechanism for moving said blade into and out of said recess to sever the wrapping between articles; the improvement wherein said blade actuating mechanism comprises means for moving said blade radially without any substantial axial motion, the cutting edge portion of said knife blade comprising a flat plate having parallel sides with a bevel formed on one side of said plate, said bevel intersection the opposite side of the plate and teeth formed in the beveled portion of the blade, said teeth having sharpened cutting edges disposed in the plane of said bevel and extending between the sides of said plate, said teeth being relieved behind said cutting edges, said sharpened cutting edges forming a sawtooth cutting edge that zig zags between the two sides of said plate for effecting progressive cutting of the web when the blade is projected into said crimping head recess for producing a zig zag severance line across the web that has the same width as the thickness of said plate. 
     
     
       10. The wrapping machine of claim 9, wherein said blade teeth have a pitch in the range of about 12 teeth/inch to 16 teeth/inch. 
     
     
       11. The wrapping machine of claim 9, wherein the blade is mounted in the crimping head so that its bevel is on the leading side of the blade. 
     
     
       12. The wrapping machine of claim 9, wherein the flat plate is about 1/32 inches thick.